The invention relates to a device for deforming, and particularly for grooving, hollow sections.
Many methods are already known for deforming plastic pipes and providing same with inner grooves.
Another drawback is that injuries to the formed groove and ring are produced as the expansible rubber ring or a ring of a like elastical material after the compressed medium has been removed therefrom often remains in contact with the pipe whereby the walls of the groove are exposed to particular undesired deformations and moreover the ring is damaged or subjected to wear.
A more serious drawback is in that with this known method the used ring of rubber or analogous material is again and again stretched with each formation of a groove, so that after about 150 groove formations the ring should be replaced.
It is also known to subject parts of pipes made of thermoplastic material, which are in a heat deformable condition, to an inner fluid pressure, whereby the part of the pipe which is subjected to the inner fluid pressure is closed by closing discs carrying at their ends, situated in the vicinity of the inner wall of the plastic pipe, expansible sealing rings. In that case a plastic made pipe is e.g. surrounded by a die provided with recesses for the formation of transverse grooves in the pipe.
In these known devices it is necessary for a continuous process that the discs with sealings enclosing the space where the plastic section should be subjected to an inner fluid pressure are movably supported on a suspension rod protruding e.g. from an extruder. After a final position has been reached the compressed medium is again caused to escape from the sealing rings, so that the assembly comprising the discs with the sealing rings can simultaneously with the dies or die halves, return to the initial position, whereupon due to expansion of the sealing rings, an inner fluid pressure can be generated in another part of the pipe.